U.S. patent application number 15/037796 was filed with the patent office on 2016-10-13 for improved noise-reducing device for tire.
This patent application is currently assigned to COMPAGNIE GENERALE DES ETA- BLISSEMENTS MICHELIN. The applicant listed for this patent is COMPAGNIE GENERALE DES ETA- BLISSEMENTS MICHELIN, MICHELIN RECHERCHE ET TECHNIQUE S.A. Invention is credited to Frederic Bourgeois, Francois-Xavier BRUNEAU, Olivier MUHLHOFF.
Application Number | 20160297259 15/037796 |
Document ID | / |
Family ID | 49949918 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160297259 |
Kind Code |
A1 |
Bourgeois; Frederic ; et
al. |
October 13, 2016 |
IMPROVED NOISE-REDUCING DEVICE FOR TIRE
Abstract
Disclosed herein is a tread for a tire, in which the tread
provides an improvement to the resonance noise-reducing devices and
seeks at the same time to obtain easy molding and demolding of the
flexible blades that form the groove closure device and complete
closure of the cross section of each groove in which these flexible
blades are formed.
Inventors: |
Bourgeois; Frederic;
(Clermont-Ferrand, FR) ; BRUNEAU; Francois-Xavier;
(Clermont-Ferrand, FR) ; MUHLHOFF; Olivier;
(Clermont-Ferrand, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMPAGNIE GENERALE DES ETA- BLISSEMENTS MICHELIN
MICHELIN RECHERCHE ET TECHNIQUE S.A |
Clermont-Ferrand
Granges-Paccot |
|
FR
CH |
|
|
Assignee: |
COMPAGNIE GENERALE DES ETA-
BLISSEMENTS MICHELIN
Clermont-Ferrand
FR
MICHELIN RECHERCHE ET TECHNIQUE S.A
Granges-Paccot
CH
|
Family ID: |
49949918 |
Appl. No.: |
15/037796 |
Filed: |
October 31, 2014 |
PCT Filed: |
October 31, 2014 |
PCT NO: |
PCT/EP2014/073486 |
371 Date: |
May 19, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60C 19/002 20130101;
B60C 2011/1338 20130101; B60C 11/1307 20130101; B60C 11/13
20130101 |
International
Class: |
B60C 19/00 20060101
B60C019/00; B60C 11/13 20060101 B60C011/13 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2013 |
FR |
1361451 |
Claims
1. A tread for a tire, comprising: a tread surface which comes into
contact with a roadway, comprising at least one groove of width W
and of depth P delimited by two lateral walls facing one another,
the two lateral walls being joined together by a groove bottom,
with at least one groove comprising: a plurality of closure
devices, each of the plurality of closure device being made up of a
flexible blade to close the at least one groove in a rest position
to a degree of closure of at least 90%, the flexible, blade having
a thickness suited to allowing it to deform under the effect of a
circulation of liquid in the at least one groove, wherein the
flexible blade is secured to the two lateral walls delimiting the
groove and is secured to the bottom of the at least one groove, and
the flexible blade, under the action of a flow of liquid, deforms
in the groove in order to reduce a degree of closure of the cross
section of this groove to at most 40%, the degree of closure being
defined as a proportion of the cross section of the groove that is
closed to the circulation of liquid.
2. The tread according to claim 1, wherein the degree of closure
when liquid is flowing is at most 30%.
3. The tread according to claim 1, wherein a length L(h) of the
flexible blade between two points at which this flexible blade is
connected to the walls delimiting a groove, the two points being
situated at a same height h measured with respect to the bottom of
the groove, and regardless of the height h, is suited to the
flexible blade--under the effect of a flow of fluid--being able to
deploy inside the groove and towards the bottom of the groove so as
to reduce the degree of closure, with the length L(h) satisfying
the following relationship:
1.5*(W+h*3.14).gtoreq.L(h).gtoreq.0.8*(W+h*3.14).
4. The tread according to claim 1, wherein the length L(h) of the
flexible blade between two points at which this flexible blade is
connected to the walls delimiting a groove, these two points being
situated at the same height h measured with respect to the bottom
of the groove, and regardless of the height h, satisfies the
relationship: 1.2*(W+h*3.14).gtoreq.L(h).gtoreq.0.9*(W+h*3.14).
5. The tread according to claim 1, wherein any line plotted on the
flexible blade and connecting all the points situated at the same
height h with respect to the bottom of the groove has a generic
shape comprising at least two undulations.
6. The tread according to claim 1, wherein any line plotted on the
flexible blade and connecting all the points situated at the same
height h with respect to the bottom of the groove has a generic
shape comprising at least one fold.
7. The tread according to claim 1, wherein the flexible blade
comprises a planar central part and connecting parts connecting
this central part on each side to the lateral walls delimiting the
groove, each lateral part forming at least one fold substantially
parallel to the said lateral walls.
Description
[0001] This application is a 371 national phase entry of
PCT/EP2014/073486, filed 31 Oct. 2014, which claims the benefit of
French Patent Application No. 1361451, filed 21 Nov. 2013, the
contents of which are incorporated herein by reference for all
purposes.
BACKGROUND
[0002] The aspects disclosed herein relate to tire treads and more
particularly to tire treads comprising grooves, the latter being
provided with closure devices so as to reduce the noise generated
by the air in these grooves going into resonance during
running.
[0003] It is known that as each groove, notably grooves of
circumferential overall orientation, enters the contact patch in
which the tire is in contact with a roadway during running, air is
made to circulate along these grooves. With the roadway each groove
forms a pipe that has two open ends.
[0004] The air in this pipe forms a vibrating air column the
resonant frequency of which is dependent on the length separating
the two ends of the pipe and therefore on the length of groove
affected by contact with the roadway.
[0005] This resonance of the air in the grooves has the effect of
generating, in a vehicle fitted with these tires, a noise inside
the vehicle and a noise outside the vehicle. These inside and
outside noises usually correspond to a frequency of 1 kHz or
thereabouts, which corresponds to a frequency to which the human
ear is particularly sensitive.
[0006] In order to reduce such resonance noise, it is known
practice (see for example patent document FR2715891), to arrange in
each circumferentially oriented groove, or groove with a
circumferential overall orientation, a plurality of relatively thin
flexible blades or membranes made of rubber compound, each flexible
blade or membrane occupying the entire cross section of the groove
or at the very least a large proportion of this cross section so as
to form a closure device.
[0007] Each flexible blade may extend from the bottom of the groove
or may be fixed to at least one of the walls delimiting the said
groove. Relatively thin here means that each flexible blade is able
to flex in order to at least partially open the cross section of
the groove under the effect of a flow of liquid notably when
driving in the wet. These same blades remain in the position in
which the groove is closed when driving in the dry.
[0008] By virtue of these flexible blades, the length of the air
column in each circumferential groove is reduced by comparison with
the overall length of groove in the contact patch, and in this
results in a change in the resonant frequency. The shift in
frequency is towards resonant frequency values to which the human
ear is less sensitive.
[0009] Of course, in order to maintain the water drainage function
needed when running on a wet roadway, notably when driving in the
wet, it is absolutely essential that this membrane be able to flex
appropriately under the action of the pressure of the water and
thus at least partially open the cross section of the groove in
order to allow a sufficient flow of liquid to circulate.
[0010] A block is a raised element formed on the tread and
delimited by voids or grooves and comprising lateral walls and a
contact face intended to come into contact with the roadway. This
contact face has a geometric center defined as being the barycenter
or center of gravity of the face.
[0011] A rib is a raised element formed on a tread, this element
extending in the circumferential direction and making a complete
circuit of the tire. A rib comprises two lateral walls and a
contact face, the latter being intended to come into contact with
the roadway during running.
[0012] A radial direction in this document means any direction
which is perpendicular to the axis of rotation of the tire; this
direction corresponds to the direction of the thickness of the
tread.
[0013] A transverse or axial direction means a direction parallel
to the axis of rotation of the tire.
[0014] A circumferential direction means a direction tangential to
any circle centered on the axis of rotation. This direction is
perpendicular both to the axial direction and to a radial
direction.
[0015] Axially towards the outside means a direction oriented
towards the outside of the internal cavity of the tire.
[0016] Equatorial plane: plane perpendicular to the axis of
rotation and passing through the axially outermost points of the
tire, this equatorial plane dividing the tire into two
substantially equal halves.
[0017] The usual running conditions of the tire or conditions of
use are those defined by the E.T.R.T.O. standard; these conditions
of use specify the reference inflation pressure corresponding to
the load bearing capacity of the tire as indicated by its load
rating and speed code. These conditions of use may also be referred
to as "nominal conditions" or "usual conditions".
[0018] A cut generally denotes either a groove or a sipe and
corresponds to the space delimited by the walls of material facing
one another and distance from one another by a non-zero distance
(referred to as the "width of the cut"). It is precisely this
distance that differentiates a sipe from a groove; in the case of a
sipe, this distance is suited to allowing the opposing walls
delimiting the said sipe to come at least partially into contact at
least in the contact patch. In the case of a groove, the walls of
this groove cannot come into contact with one another under normal
running conditions.
[0019] The tread surface of a tread corresponds to the surface of
the tread that comes into contact with the ground when a tire
provided with such a tread is being driven on.
[0020] As was recalled earlier, the devices formed of flexible
blades and described in the prior art--on account of the need to be
able to flex under a flow of liquid--are connected either to the
bottom of a groove or to one of the lateral walls delimiting a
groove. However, a space remains either between the walls and each
blade or between the bottom and each blade, thereby reducing the
expected resonance noise reduction performance.
[0021] In order to address this problem, an earlier patent
application, not yet published at the date of filing of the present
application, has proposed forming small cuts or grooves in the
bottom of a groove and on the walls delimiting this groove so that
a blade can be inserted into these small cuts, thereby obtaining
complete closure of the groove. While this solution is effective
because it allows the groove to be completely closed, it
nevertheless remains expensive to implement.
[0022] Document JP-H04 221207 A discloses a device comprising two
disjointed blades, each blade being fixed to one wall and partially
to the bottom of one and the same groove. There still remains
between these two blades a space which is not closed and the noise
performance can therefore be improved further.
[0023] There is a need to obtain a device that reduces resonance
noise in the grooves that is simpler to implement and more
economical.
[0024] The expression "wall bearing a blade" is to be interpreted
in the present document as meaning one or other of the lateral
walls delimiting a groove, the blade forming the noise-reducing
device being secured to each lateral wall and to the bottom of the
groove.
SUMMARY
[0025] The present disclosure is an improvement to the resonance
noise reducing devices and seeks at the same time to obtain easy
molding and demolding of the flexible blades that form the groove
closure device and complete closure of the cross section of each
groove in which these flexible blades are formed.
[0026] To this end, the subject of the disclosure is a tire tread,
this tread having a tread surface intended to come into contact
with a roadway and comprising at least one groove of width W and of
depth P delimited by two lateral walls facing one another, these
lateral walls being joined together by a groove bottom, at least
one groove comprising a plurality of closure devices, each closure
device being made up of a flexible blade to close this groove in a
rest position to a degree of closure of at least 90%, each blade
having a thickness E suited to allowing it to deform under the
effect of a circulation of liquid in the groove.
[0027] This tread is such that this flexible blade is secured to
the two lateral walls delimiting the groove and is secured to the
bottom of this groove, and such that each flexible blade is
dimensionally suited to be able, under the action of a flow of
liquid, to deform elastically in the groove and towards the bottom
of the said groove in order to reduce its degree of closure of the
cross section of this groove to at most 40%.
[0028] A flexible blade is said to be secured to the walls and to
the bottom of a groove when it is connected fixedly to these walls
and to the bottom unlike the flexible blades employed in the prior
art which are connected only to the bottom of a groove or
alternatively to one of the walls of a groove. Under the action of
a liquid flowing in the groove provided with a device according to
the disclosure, the flexible blade flexes and, while remaining
secured to the lateral walls and to the bottom, deploys allowing
the flow of liquid to pass as a result of predetermined dimensions.
When the flow of liquid is interrupted, the flexible blade reverts
to its non-deformed initial position by virtue of the elastic
return generated by the material of which the blade is made. In
general, this material is the rubbery material of which the tread
is made.
[0029] The degree of closure of a flexible blade here means the
portion, expressed as a percentage, of the cross section of the
groove provided with such a flexible blade. A degree of closure
equal to 100% means that the cross section is completely closed by
the flexible blade.
[0030] Obtaining a degree of closure at most equal to 40% when the
flexible blade is subjected to the action of a flow of liquid means
that 60% of the cross section is open and allows this liquid to
circulate. This percentage is measured when the tire is new, which
indeed corresponds to the state in which the greatest amount of
resonance noise is generated.
[0031] For preference the degree of closure when the blade is
deformed under the action of a flow of liquid is at most 30% and
more preferably still 20%.
[0032] Advantageously, when the flexible blade is deformed, the
degree of closure is as small as possible--which means to say as
close as possible to 0%--so that the wet-running performance is
maintained until the tire is fully worn down to the regulation
tread wear limit.
[0033] When considering the length. L(h) of the flexible blade
between two points at which this flexible blade is connected to the
walls delimiting a groove, these two points being situated at the
same height h measured with respect to the bottom of the groove (if
the bottom is curved then the height h is considered with respect
to the innermost point of the bottom when viewed in cross section),
it is advantageous for this length L, and regardless of the height
h, to be determined so that the flexible blade--under the effect of
a flow of fluid--can deploy inside the groove and towards the
bottom of this groove so as to reduce the degree of closure at most
to 40% and, more preferably still, at most 30% or even 10%, or even
0%.
[0034] For preference, the flexible blade has a length L(h) for a
height h which is chosen so as to satisfy the following
relationship:
1.5*(W+h*3.14).gtoreq.L(h).gtoreq.0.8*(W+h*3.14).
[0035] More preferably still, the length L(h) of the flexible blade
between two points at which this flexible blade is connected to the
walls delimiting a groove, these two points being situated at the
same height h measured with respect to the bottom of the groove,
and regardless of the height h, satisfies the relationship:
1.2*(W+h*3.14).gtoreq.L(h).gtoreq.0.9*(W+h*3.14).
[0036] For preference, the flexible blade of the noise-reducing
device is perpendicular to the main direction of the groove (this
direction corresponds to the direction in which water flows when
driving in the wet).
[0037] The total height of a flexible blade is denoted H: this
height H corresponds to the length measured between the bottom of
the groove and those points of connection to the lateral walls that
are furthest from the bottom of the groove.
[0038] This noise-reducing device may of course be used with any
type of groove, whether this be a groove of circumferential,
transverse or oblique orientation.
[0039] In one alternative form, a noise-reducing device comprises a
blade formed of a central part and, on each side of this central
part, connecting parts for connecting with the lateral walls
delimiting the groove, each connecting part comprising at least one
fold.
[0040] In another alternative form, any line plotted on a flexible
blade and connecting all the points situated at the same height h
with respect to the bottom of the groove has a generic shape
comprising at least two undulations. An undulation here means a
shape diverging from the straight line connecting the two points of
connection of the blade with the walls delimiting the groove at the
height h. This undulation may take the form of a succession of
segments forming a broken line.
[0041] The elastic nature of the material of each flexible blade
also creates elastic return forces to ensure that the blade returns
to its position in which the groove is closed when there is no
longer any flow of liquid in the said groove.
[0042] The disclosure also relates to any tire provided with a
tread comprising a noise reducing device formed of a flexible blade
to close this groove in the rest position to a degree LS of closure
which is equal to 90%, each blade having a thickness E suited to
allowing it to deform under the effect of a circulation of liquid
in the groove.
[0043] Further features and advantages of the disclosure will
become apparent from the description given hereinafter with
reference to the attached drawings which, by way of nonlimiting
examples, show embodiments of the subject matter of the
disclosure.
BRIEF DESCRIPTION OF THE FIGURES
[0044] FIG. 1 shows an alternative form according to the disclosure
of a noise-reducing device in the closed state for preventing air
from circulating;
[0045] FIG. 2 shows the alternative form of FIG. 1 in a partially
open position for allowing a liquid to flow;
[0046] FIG. 3 shows a cross section of the groove closed off by the
closure device according to the alternative form shown in FIG.
1;
[0047] FIG. 4 shows a cross section of the groove which is
partially open under the effect of a flow of liquid as shown in
FIG. 2;
[0048] FIG. 5 shows a surface view of a second alternative form
according to the disclosure of a closure device, this device being
formed of a planar central part and of connecting parts for
connecting with the lateral walls delimiting the groove that form
folds;
[0049] FIG. 6 shows a surface view of the second alternative form
according to the disclosure in a deployed position to open the
cross section of the groove.
DETAILED DESCRIPTION
[0050] In the figures that accompany this description, the same
reference signs may be used to describe alternative forms of the
disclosure where these reference signs refer to elements of a
similar nature, whether this nature be structural or indeed
functional.
[0051] FIG. 1 shows an alternative form according to the disclosure
of a noise-reducing device in the closed state for preventing air
from circulating.
[0052] This FIG. 1 shows a groove 2 of circumferential overall
orientation formed on the tread 1 of a tire. This groove of width W
is delimited by lateral walls 21, 22 of raised elements, these
lateral walls facing one another being connected by a groove bottom
20. This groove 2 has a depth P, when new, that is to say prior to
any running and therefore before any wear. The tread comprises a
tread surface 10 intended to come into contact with the roadway
during running.
[0053] Formed in this groove 2 are a plurality of devices that
counter resonance noise, each device being made up of a blade 3 of
flexible rubber of the same nature as the material of which the
raised elements of the tread are made. This flexible blade 3 is
secured to the lateral walls 21, 22 delimiting the groove and to
the bottom 20 of the groove. Moreover, each flexible blade 3 in the
rest position and when new closes the entire groove so as to
prevent any circulation of air during running. Rest position here
means a state of the tire that is not loaded in running.
[0054] In this alternative form, the flexible blade 3 is
dimensioned so as to be able to flex under the action of pressure
generated by a flow of liquid notably when running on a wet
roadway.
[0055] FIG. 2 shows the alternative form of FIG. 1 in a partially
open position so as to allow the flow of a liquid indicted
schematically by an arrow F. In this position, and when new, the
cross section of the groove 2 is partially open (in this instance
at least 60% of the cross section of the groove is open) so as to
allow liquid to circulate when running on a wet roadway.
[0056] It is of course preferable for the flexible blade 3 in its
open position for allowing liquid to circulate to close the cross
section of the groove 2 in which it is placed as little as
possible.
[0057] FIG. 3 shows a view in cross section of the groove 2 closed
off by the closure device according to the alternative form
depicted in FIG. 1.
[0058] It may be seen that the flexible blade 3 in its closed
position is connected to each lateral wall 21, 22 delimiting the
groove and to the bottom 20 of this groove. The flexible blade 3
has a total height H which in this instance is equal to the depth P
of the groove when new. This flexible blade has a mean thickness of
2 millimeters.
[0059] In order to allow the blade 3 to flex in the groove and thus
open the cross section of this groove, the lengths L(h1), L(h2) and
L(H) each satisfy the following relationship:
1.5*(W+h*3.14).gtoreq.L(h).gtoreq.0.8*(W+h*3.14)
[0060] FIG. 4 shows a view in cross section of the groove 2 shown
in FIG. 3 when liquid is flowing in this groove. Under the action
of the pressure of the liquid circulating in the groove, the
flexible blade 3 develops in the groove to open the cross section
of the groove.
[0061] FIG. 5 shows a surface view of another alternative form
according to the disclosure of a device for the closure of a groove
(2) delimited by lateral walls 21, 22 intersecting the tread
surface at edges and a groove bottom 20 connecting the said lateral
walls. This closure device is formed of a flexible blade 3
comprising a planar central part 31 connected to the bottom 20 of
the groove and, on each side of this central part 31, two
connecting parts 32 securely connecting the flexible blade to the
lateral walls delimiting the groove.
[0062] Each connecting part 32 forms two folds 321, 322 which are
substantially parallel to the lateral walls 21, 22. The developed
lengths of these connecting parts combined with the length of the
central part are suited to allowing at least partial opening of the
groove under the effect of a flow of liquid.
[0063] It is entirely possible to form just one fold or more than
two folds for each connecting part provided that the condition
whereby the length L(h) measured between two points of connection
of this flexible blade to the walls delimiting a groove, these two
points being) situated at the same height h measured with respect
to the bottom of the groove, and whatever the height h, is chosen
to satisfy the following relationship:
1.5*(W+h*3.14).gtoreq.L(h).gtoreq.0.8*(W+h*3.14),
is met,
[0064] W corresponding to the width of the groove on the tread
surface when new.
[0065] FIG. 6 shows a surface view of the tread depicted in FIG. 5
in a configuration in which the flexible blade is deployed into the
groove to open the cross section of this groove and allow liquid to
circulate. In this configuration, the folds are unfolded so that
the blade 3 can deploy into the groove and at least partially open
the cross section.
[0066] While the disclosure has been described in general terms and
using a number of alternative forms, it must be appreciated that
this disclosure is not restricted to these alternative forms
described and depicted alone. Notably, when the lateral walls
delimiting a groove make an angle other than 90 degrees to the
tread surface when new, it is easy for those skilled in the art to
adapt the lengths L(h) of each blade to allow an opening of the
cross section of the groove. Furthermore, the alternative forms
described here may be combined with one another by those skilled in
the art according to the objective being pursued, without departing
from the scope of the disclosure as defined by the claims.
* * * * *